My kinder said that they are not legally allowed to refuse kids on basis of toilet training, but encourage parents to do so, and they may call you up to change the child if they poo.

you could try encouraging her to sit in the bathroom, or on the toilet (wearing a nappy) when she poos. I have also heard people have success by then cutting bigger and bigger holes in the nappy (disposable), so eventually the poo goes into the toilet.